/usr/share/kservices5/searchproviders/upackage.desktop is in kubuntu-web-shortcuts 17.04ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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Charset=
Hidden=false
Keys=upackage,upkg
Name=Ubuntu Packages
Query=http://packages.ubuntu.com/search?keywords=\\{@}&searchon=names
ServiceTypes=SearchProvider
Type=Service
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